A tradition in notorious student party town Dunedin, New Zealand. Involves dressing up in a group with a common theme, drinking very early in the morning (and continuing all day) and making your drunken way to the Cook bar for a day full of drinking.

Is now banned from Dunedin thanks to the university opposing the liquor renewal of the Cook.

Guy 1: Bro, what you going to cookathon as?
Guy 2: Our flats going as terrorists. What about you?